Spin crossover micro and nanoparticles embedded in various environments: an experimental and theoretical study
(Micro și nanoparticule cu tranzitie de spin încorporate in diverse medii: studiu experimental si teoretic)
Financed by the Romanian National Authority for Scientific Research, CNCS – UEFISCDI, project PN-II-RU-TE-2014, no. 151 / 2015
Project Director: Conf. univ. dr. Cristian ENACHESCU
(Faculty of Physics, Alexandru Ioan Cuza University, Iași)
The project is devoted to the study of fundamental properties of nano and micro structured spin-crossover (SC) materials embedded in various media. These compounds, having two spin states with different magnetic and optical properties, are intensely studied due to their potential use in technological applications, as data storage or sensors and actuators. As the molecules also have different volumes in the two states, the SC materials are dominated by elastic interactions which trigger multi-hysteretic behavior induced by temperature, pressure or light. In addition, some micro and nanoparticles of SC materials embedded in polymers or surfactants show a huge hysteresis of mechanical nature. Their behaviour is not only influenced by the environment, but equally, in core-shell structures, the transition of shell SC materials could influence the piezoelectric properties of core materials. Therefore, the SC nanoparticles embedded in various media are interesting for potential applications due to their intrinsic properties but also due to the mechanical influence on environment. The present research will have two main directions: one experimental and the other of modeling. The experimental study of the mentioned compounds will include magnetometric and optical measurements. The experiments will be closely accompanied by a modeling effort using Monte Carlo approaches which will cover the domain from the molecular level up to and nano and microstructures.
The aim of the project is to understand the behaviour of spin crossover micro and nano particles interacting with the environment, in order to handle and apply the properties of the bistability and switching of these materials at meso and nanoscale. The long term perspective consists in clarifying the possibilities of their application for the storage of high density information, or for their use as sensors and actuators. The systematic experimental studies will be correlated and interpreted by the simultaneous use of theoretical and numerical studies. The theoretical studies will be based on the experimental data and will be used not only to explain the observations, but also for correcting the experiments and to propose new experimental procedures.
The idea of this scientific project is centred on the study of spin crossover micro and nanoparticles dispersed in various environments, either polymeric for the beginning or piezoelectric in a second stage. This idea is based on the fact that the behaviour of micro and nanoparticles embedded in various matrices is totally different comparing to free micro and nanoparticles. Due to the change of volume during the transition, not only the spin crossover compound is influenced, but also the environment. Therefore, its eventual piezoelectric properties could be controlled by the state of spin crossover compound. The hypotheses suggested by some of our preliminary results show that the effects could depend on the volume change of the particles, on elastic interactions between the particle and the molecules composing the matrices (as van der Waals forces) and on the properties of the matrix (rigidity, density, fragility, viscosity, relaxation dynamics etc)